TECHNICAL issues with the fourth Astute-class submarine have resulted in a 17-month delay in the boat entering service.

Audacious, the fourth of seven vessels due to be delivered under the £11 billion Astute-class programme, was supposed to have entered service in summer.

The operational handover of Audacious to the Royal Navy has been delayed by 17 months due to technical issues in production.

An MOD spokesperson said: "The Audacious operational handover delay has been caused by technical issues."

But they said it remains committed to delivering all seven Astute-class vessels by the end of 2026, and that HMS Audacious 'is expected to commence sea trials by the end of this year'.

The Ministry of Defence refused to reveal what faults had caused the delay because of a risk of jeopardising security and capability.

Similar delays could now be experienced in the delivery of Anson, another Astute-class vessel, costing £1.3 billion.

Set-backs in the timings of the delivery to the Royal Navy have not caused the programme to overrun in costs, according to the MOD.

Sir Stephen Lovegrove, permanent secretary at the MOD, revealed the technical issues with Audacious in a letter to Meg Hillier, the Labour chair of the Commons public accounts committee this month.

He wrote: “The emergent issues have required unplanned repair and rework to facilitate the submarine proceeding forward with the normal commissioning process.”

The MoD may have to extend the November 2026 deadline for the delivery of all seven vessels, he said.